Abstract
BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) is sensitive to the cerebral manifestations of human prion diseases. The magnitude of diffusion weighting, termed “b factor,” has only been evaluated at the standard b = 1000 s/mm2. This is the first rigorous evaluation of b = 2000 s/mm2 in Creutzfeldt-Jakob Disease (CJD).
MATERIALS AND METHODS: We compared DWI characteristics of 13 patients with CJD and 15 healthy controls at b = 1000 s/mm2 and b = 2000 s/mm2. Apparent diffusion coefficients (ADC) were computed and analyzed for the whole brain by voxel-wise analysis (by SPM5) as well as in anatomically defined volumes of interest (by FSL FIRST).
RESULTS: Measured ADC was significantly lower (by approximately 5%–15%) at b = 2000 s/mm2 than at b = 1000 s/mm2 and significantly lower in patients than in controls. The differences between patients and controls were greater and more extensive at b = 2000 s/mm2 than at b = 1000 s/mm2 in the expected regions (thalamus, putamen, and caudate nucleus).
CONCLUSIONS: Because higher b factors change the absolute value of observed ADC, as well as lesion detection, care should be taken when combining studies using different b factors. While the clinical application of high b factors is currently limited by a low signal intensity–to-noise ratio, it may offer more information in questionable cases, and our results confirm and extend the central role of diffusion imaging in human prion diseases.
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